The present invention relates to an apparatus for feeding a stack of individual cut sheets of flat flexible media such as paper, vellum, transparencies or the like to a single sheet separator roller of a document handling device such as a scanner, facsimile machine, printer or copier and combinations of such devices. The teachings of the invention are applicable generally to any office or business machine which uses a stack of flexible media sheets which are to be fed to the machine one at a time.
Inexpensive document processing apparatus typically requires the user to place a stack of documents to be processed into the apparatus for delivery to the nip of the single sheet separator. The skill (or carelessness) of the operator determines the frequency of improper placement of the stack into the document processing apparatus. If the stack is improperly placed, as by inadvertently skewing or fanning the leading edges of the individual document sheets or by pushing the stack too far into the nip, the single sheet separator more frequently may engage and pick the wrong sheet or it may pick multiple sheets simultaneously. Accordingly, it is an object of the present invention to provide an automatic document feeder for moving a stack of individual sheets from a stack loaded position to the single sheet separator so that the operator can load the stack against an automatic document feeder rather than directly against the single sheet separator mechanism where misfeeds due to improper stack loading may occur.
The present invention provides an automatic document feeder for moving a stack of individual sheets from a stack loaded position to a nip in a single sheet separator in a document processing apparatus comprising:
a) a pre-pick roller support shaft having spaced support bearings thereon;
b) a pre-pick roller rotatably supported on said shaft, said pre-pick roller having a sheet gripping surface thereon;
c) a pressure plate resiliently biased toward said sheet gripping surface to urge a stack of sheets against said sheet gripping surface of said pre-pick roller;
d) a stack stop rotatably mounted on said shaft, said stop having at least one finger moveable between a stack blocking position in which said finger contacts said pressure plate to move said pressure plate away from contact with said pre-pick roller and a stack transmitting position in which said finger no longer contacts said pressure plate;
e) a source of rotary power connected to said shaft for rotating said pre-pick roller support shaft in a reverse reset direction and in a forward sheet delivery direction; said pre-pick roller support shaft and said pre-pick roller having mutually engageable drive stops thereon positioned such that said pre-pick roller is: (1) freely rotatable on said shaft during loading of a stack in contact with said pre-pick roller into engagement with said finger and when said shaft is driven in said forward direction to move said finger from an initial stack blocking position to a stack passing position; and (2) rotated by said rotating shaft during shaft rotation in said forward direction until a leading edge of said stack has reached said nip.
The present invention further provides a document processing apparatus comprising a document processing section, a single sheet separator having a stack receiving nip and an automatic document feeder wherein said automatic document feeder comprises:
a) a pre-pick roller support shaft having spaced shaft support bearings thereon;
b) a pre-pick roller rotatably supported on said shaft, said pre-pick roller having a sheet gripping surface thereon;
c) a pressure plate resiliently biased toward said sheet gripping surface to urge a stack of sheets against said sheet gripping surface of said pre-pick roller;
d) a stack stop rotatably mounted on said shaft, said stop having at least one finger moveable between a stack blocking position in which said finger contacts said pressure plate to move said pressure plate away from contact with said pre-pick roller and a stack transmitting position in which said finger no longer contacts said pressure plate;
e) a source of rotary power connected to said shaft for rotating said pre-pick roller shaft in a reverse reset direction and in a forward sheet delivery direction; said pre-pick roller support shaft and said pre-pick roller having mutually engageable drive stops thereon positioned such that said pre-pick roller is: (1) freely rotatable on said shaft during loading of a stack in contact with said pre-pick roller into engagement with said finger and when said shaft is driven in said forward direction to move said finger from an initial stack blocking position to a stack passing position; and (2) rotated by said rotating shaft during shaft rotation in said forward direction until a leading edge of said stack has reached said nip.